1. Field of the Invention
The present invention is directed to a process for the preparation of dihalovinyl compounds.
2. Description of the Prior Art
2-(2,2-Dihalovinyl)-3,3-dimethylcyclopropyl compounds and 1,1-dihaloalkene compounds are known intermediates in the preparation of known cyclopropanecarboxylate pyrethroid esters of U.S. Pat. No. 4,024,163.
These pyrethroids show remarkable activities against various insects. Moreover these compounds show very low mammalian toxicity which makes them extremely useful as pesticides for crop protection. Thus bollworm species which infest cotton and cotton leaf worms which are leaf-eating pests are effectively combatted with pyrethroids. Pyrethroids have shown their usefulness as pesticides for fruit and vegetable protection.
Also for animal health protection pyrethroids can successfully be applied. For example against red mites which are found in the cracks and crevices of poultry houses, particularly on perches, and which cause loss of condition by feeding on the blood of the birds. Another application of pyrethroids is against some kinds of beetles which may cause serious structural damage to buildings especially those containing wood or polystyrene. The proved usefulness of pyrethroids stimulates Research and Development to find novel intermediates and novel economic routes to pyrethroids. It is the object of the present invention to provide a process for preparation of useful 2,2-dihalovinyl compounds.
From U.S. Pat. No. 4,018,838 a process for the preparation of dihalo-substituted alkene pyrethroid intermediates is known. The process comprises the reductive dehydrohalogenation of alpha-haloalcohols to give dihalo-substituted alkenes using zinc dust and acetic acid.
The present process obviates the use of zinc and acetic acid in the preparation of the dihalovinyl compounds which make this process not only novel but also economically and technically attractive.